Unconventional computing

Unconventional computing is computing by a wide range of new or unusual methods. It is also known as alternative computing. The different methods of unconventional computing include optical computing, quantum computing, chemical computing, natural computing, biologically-inspired computing, wetware computing, DNA computing, molecular computing, amorphous computing, nanocomputing, reversible computing, ternary computing, fluidics, analogue computing, and Domino Computation.

Historically, mechanical computers were used in industry before the advent of the transistor. Mechanical computers retain some interest today both in research and as analogue computers. Some mechanical computers have a theoretical or didactic relevance, such as billiard-ball computers or hydraulic ones, and are actually simulated. (No attempt is made to build a functioning computer through the mechanic collisions of billiard balls.) The Domino computer is another theoretically interesting mechanic computing scheme.

Unconventional computing is, according to a recent conference description, "an interdisciplinary research area with the main goal to enrich or go beyond the standard models, such as the von-Neumann computer architecture and the Turing machine, which have dominated computer science for more than half a century". These methods model their computational operations based on non-standard paradigms, and are currently mostly in the research and development stage. This computing behavior can be "simulated" using the classical silicon-based micro-transistors or solid state computing technologies, but aim to achieve a new kind of computing engineering inspired in nature.

Mechanisms

Billiard balls (billiard ball computer); this is an unintuitive and pedagogical example that a computer can be made out of almost anything.

Light (optical computing)

Computers can manipulate information as light (rather than electricity or billiard balls).

Molecules (DNA computing, chemical computing)

Gears, levels, dials, etc. (analog computer/mechanical computers)

Neurons (wetware computer)

Fluid (fluidics)

Agents acting under a special set of rules (cellular automata)

People acting under a set of rules can be part of a computer; example. If the "agent" was a human, it would not be major part of the computer, exactly like a single neuron is not an entire brain system.

Quantum mechanics (quantum computing)

(source:wikipedia)